I think the Latin expression "omnia" is equal to "the whole world", "everybody", "everyone" etc.
and it becomes tautological to say "Omnis mundus", I would have excluded "mundus" as it isn't a geographical expression.
I was talking with Menininha in PVT. I helped her with this one, but I just found that "to lie" in Latin is one of that annoying deponent verbs, "mentior". Therefore, for the good of the game, the translation should be corrected to "Omnia mentiuntur".